Ending child marriage could return more than US$ 4 trillion to the global economy, according to this new study. 15 million girls under 18 are married every year – putting good education and jobs out of reach for many. The practice also leads to increased population growth; data from 15 countries with high child marriage rates show that girls married at age 13 will have 26% more children than if they married at 18 or later. Globally, the rate of child marriage is declining, but every 3 seconds a girl under 18 gets married.